Facsimile system



NOV. 10, 1936. w G FlNcH 2,060,778

FACSIMILE SYSTEM Filed Nov. 11, 1935 5 Sheets-Sheet 1 AMPLlFI I R. F. OSCILLATOR AMPLIFIER AMPLIFI ER BEAT FREQUENCY OSCILLATQR INVENTOR. willz'anjflfp z'nch ATTORNEY.

Nov. 10, 1936. w. G FINCH 2,060,778

FACSIMILE SYSTEM Filed Nov. 11, 1935 5 Sheets-Sheet 3 osuLLATOR fig: 4 q

AMPLIFIER RECEIVER 68 70 66 1 5 e7 SPEAKER z INVENTOR. willidfijjifgii'fltb ATTORNEY.

Nov. 10, 1936.

W. G. H. FINCH FACSIMILE SYSTEM Filed NOV. 11, 1935 5 Sheets-Sheet 4 04 05 J05 J5Z- a 54 6 126 108 v 151 151 f Illlllll 5; 125 21 Hg: '7 29 #122:

RECEIVER 70 INVENTOR.

'wizzz'am 96 522);

ATTORNEY.

Patented Nov. 10, 1936 UNITED STATES PATENT OFFICE 7 Claims.

My invention relates to novel apparatus for and methods of transmitting and reproducing pictures or the like.

In the transmission of shaded pictures, a beam of light is caused to scan the picture and then impinge upon a photo-sensitive cell, the intensity of the impinging beam varying in accordance with the shading of the picture. A chopper wheel placed in the path of the light beam to interrupt it at a uniform rate, or equivalent methods are used so that alternating current rather than di-.-

rect current amplifiers may be employed. The

amplified impulses modulate a carrier wave for radio broadcasting thereof. The broadcast signal is accordingly modulated at a. fixed frequency at varying amplitude. A radio receiver detects the modulation of the radiated signals to actuate a suitable picture recording element. In order to reproduce the original shaded figure, the detected 2 signals must faithfully represent the original amplitude modulated signals. vagaries of radio broadcasting transmission, particularly fading, distort the received signals to destroy the relative amplitudes of the actuating recording impulses 25 in the reproduction of the shaded figure being transmitted.

I have invented novel apparatus for convert- -ing the varying light intensities of the beam which impinges upon the photo-electric cell to 30 signals having a constant amplitude but of frequency varying in accordance with the intensity of the impinging beam. These signals may be transmitted directly over a wire line circuit or may be used to modulate a radio frequency car- 35 rier wave for radio transmission. An ordinary radio receiver is used to detect these constant amplitude signals of varying frequency, and made to actuate well known recording means, or to operate the simple, novel, efficient reproducing 40 units which also form part of my present invention. The reproduced picture is built up by a plurality of short marking impulses. These impulses compose a figure which is shaded in accordance with the transmitted picture. The 45 higher the frequency of the actuating signal,

the greater will be the number of marking impulses in a given time, and a darker picture element is recorded.

Pictures reproduced according to my invention 50 are composed of a multiplicity of individual impulses or dots, and may therefore be directly used as half-tone reproductions such as for newspaper printing. My invention is directly applicable for actuating an engraver for directly cutting a zinc 5 plate which may be used in printing presses and the like for picture printing. Half-tone processes are generally used for breaking up an original photograph into elemental units to avoid ink blurs and to permit finer detail in the printing of pictures. My present facsimile system transmits and reproduces pictures composed of individual impulses. The reproduced picture, having any predetermined detail, may in turn, be directly used for picture printing in newspaper work, or for local perception of the transmitted visual messages or pictures.

Another important feature of my invention is to employ any system of facsimile transmission where the shading of the picture is caused to vary the amplitude of the facsimile signal being transmitted, receive and detect these signals at a distance, and convert them to impulses of constant intensity but of frequency varying in accordance with the original shading of the picture being transmitted. An important resultant advantage is that the major portion of the energy for the printing impulses is generated locally at the receiving station, and. the detected signals are used to merely vary the frequency of the said local impulses. I thus provide a simple, rugged, emcient and cheap facsimile reproducing mechanism. The novel reproducing units according to my invention, are useful where direct actuation for half -tone reproduction is desired whereby the picture is built up of discrete impulses, as hereinabove explained. Such a rugged system, which is light in weight, is also particularly useful for aircraft facsimile receivers.

For many applications, it is only necessary to transmit figures which may be built up by merely black and white impulses as, for example, printed or written matter, sketches, unshaded drawings and the like. I provide novel, simple methods for reproducing such black and white pictures wherein the major energy of the marking impulses is locally produced. Accordingly, it is an object of my invention to provide novel methods for transmitting facsimile signals. 7

Another object of my invention is to provide novel methods for transmitting facsimile signals of constant amplitude but of frequency varying in accordance with the shading of the picture being transmitted.

It is still another object of my invention to provide novel apparatus for converting varying light intensities to signals of constant amplitude but varying frequency.

A further object of my invention is to provide a novel method for reproducing a transmitted picture as a series oi marking impulses of varying spacing.

Still a further object of my invention is to provide a novel method for converting amplitude modulated facsimile signals to signals having constant amplitude of varying frequencies.

Another object of my invention is to provide novel methods for producing facsimile marking impulses locally and controlling the frequency of said impulses in accordance with received facsimile signals.

A further object of my invention is to provide novel facsimile reproducing apparatus that is simple, rugged, efllcient and cheap.

There are other objects of my invention, together with the foregoing, which will appear in the detailed description to follow in connection with the drawings, in which:

Figure 1 is one modification of a facsimile transmitting system according to my invention.

Figures 2 and 2a are further modifications for a facsimile transmitting system according to my invention.

Figure 3 is a facsimile receiving system for use with the transmitters of Figures 1 and 2.

Figure 4 is a schematic illustration of a wellknown facsimile transmitting system which may be used for the following several modifications of facsimile receiving systems according to my invention.

Figure 5 illustrates one modification of a facsimile reproducing system according to my invention.

Figure 6 schematically illustrates a modification of the reproducing unit of Figure 5.

Figure 7 is a sectional elevation of a preferred embodiment of a reproducing unit illustrated in Figure 6.

Figure 8 is another modification of a facsimile reproducing system according .to my invention.

Figures 9 and 10 are further modifications of facsimile reproducing systems for black and white pictures or messages.

Referring to Figure 1, I have schematically indicated a method used for varying the intensity of light impinging upon the photo-electric cell I in accordance with the shading of a picture I mounted on a drum 3. Light from a source I is concentrated to a point which is directed along the picture I in a predetermined manner. Light is reflected from the surface in varying intensity according to the shading of the picture being scanned. Thus, as a white portion of the picture is passed over, a maximum of light is reflected and made to impinge upon the photosensitive surface of the photo-electric cell I along the reflected beam I in a well-known manner. When a darker portion of the picture is traversed, correspondingly less light is reflected to the photo-sensitive cell I. The light intensity of the reflected beam 5 is accordingly varied in proportion to the shading of the spot on the picture I which the light from the source I is scanning. Other methods of scanning a picture for transmission may equally well be used. For example, the light source I may be mounted within the drum I, the picture I be translucent, and light is transmitted through it of intensity varying with the shading on it.

When a drum is used, the length of the picture is limited. There are several methods and systems where the pictures or messages to be transmitted are on a long sheet which is continuously advanced through the scanning mechanism, which may, of course, also be used with my present invention. Such a system is disclosed in my Reissue Patent No. 19,575 of May 21,

1935. The light beam I of varying intensity produces fluctuations in the current passing through the photo-electric cell I which is connected to the direct current amplifier I of the push-pull type. The output 1 of the amplifier I is connected to the solenoid I which acts upon plunger I. The push-pull direct current amplifier I is preferably of the type disclosed in my co-pending application Serial No. 49,221, filed Nov. ll, 1935. The output stage of the direct current amplifier I is arranged to fully energize coil Ib of the solenoid I when no signal appears at the input to the amplifier I, and corresponds to a black segment being scanned on picture I. When a signal is introduced to the amplifier I, coil Ia. is proportionately energized, while the current through coil lb is correspondingly decreased. The plunger is thereby attracted up towards coil Ia. The circuits are designed to cause the plunger I to be in its lowest position when a black picture segment is scanned; to be attracted to its highest position in the solenoid I when a white segment is scanned; and to assume intermediate positions in accordance with the shading of the picture segments.

The plunger I is made of soft iron and is preferably laminated to reduce hysteresis and eddy current losses. I have illustrated a spring II pressing against a transverse pin II fastened at the end of the plunger 8, for mechanically biasing the plunger and steadying its movements. A metallic projection II of the plunger I passes through the portion II of the insulation structure II. A contact point II is formed at the end of the projection II. An electro-magnet II is arranged to attract an annature II when current passes through it. The armature I1 is connected to a flexible spring II which is fixedly mounted In the post I I. A contact spring III attached to the top face of the armature II as shown, coacts wi the contact II.

The local electro-mechanical circuit II, comprises a battery or direct current source II, connection II to the electro-magnet II, lead II to the metallic post I9 and metal spring II, metallic armature I1, contact spring II, contact point II,

lead II flexibly connecting projection II (and contact II) to rheostat II, and lead II to primary 21 of transformer II and lead "to battery II. When the contact point II touches the contact spring III, it closes the local electrical circuit II and current flows through the electro-magnet II causing it to attract the armature II, in turn breaking the electrical contact between spring II and point II when the electro-magnet II releases its attraction for the armature II which returns to cause re-contacting of point II and spring II to repeat the cycle.

The frequency of vibration oi the armature II depends primarily on its mass, the elasticity of spring I8 and the distance it must travel in order to re-contact with the point II. The rheostat II is used to control the operating current flowing in this local circuit. As the circuit is completed by the contact point I5 and contact spring II, an electrical impulse passes through the local circuit 30 and is transmitted by the primary 2'! of the transformer II to its secondary winding II. As contact point II is raised, the frequency of vibration of the armature I1 is reduced since the armature I I has a greater amplitude of vibration and takes more time per vibration. Time frequency of interruption of the local circuit is accordingly reduced and the impulses transmitted to the secondary 3| of the transformer 23 are of the same frequency. The action of the local electro-mechanical circuit 30 which I have herein disclosed is analogous to the action of an ordinary buzzer, and the variation ofthe distance of the contact point l5 corresponds to the adjustment of pitch orvibration frequency of said buzzer. However, I employ this simple means for translating facsimile signals of varying amplitudes to impulses of constant amplitudes and varying frequencies in the following manner:

The facsimile signals introduced to the solenoid 3 causes a varying attraction for the plunger 9 within said solenoid 8 as hereinbefore explained. When a strong signal is introduced to amplifier 8, the plunger 9 is moved nearer to the vibrating armature H. The frequency of vibration of the armature I1 is thereby increased, and the frequency of the impulses induced in the secondary ll of the transformer 28 is likewise increased.

moves away from the armature l1 decreasing the frequency of vibration of said armature l1 and causing a lower frequency of impulses to be induced in secondary winding 3|. I

I provide a mechanical stop I3 mounted in member Hi to limit the amplitude of excursion of the armature [1 from the electro-magnet IS a predetermined amount. An excess of upward attraction for the plunger 9, caused by a white spot being scanned on picture 2, will move the contact point l5 beyond contacting relation with the spring 20 due to the limitation in the excursion of the armature I! by the stop l3. No impulses will therefore be transmitted to the secondary 3| while white areas of the picture are being transmitted. Intermediate positions of the plunger 9 in, the solenoid 8 are due to intermediate shadings of the picture 2 segments which produce corresponding intermediate amplitudes of signal input to the amplifier 6. The contact point I5 will assume intermediate positions and corresponding variations will occur in the frequency of vibration of the armature l1. Darker areas will produce higher frequencies, and lighter areas will produce lower frequencies of impulses induced in the secondary winding 3| of transformer 23.

The amplitude of the induced voltage impulses will be substantially constant but the frequency will vary in accordance with the shading of the picture being transmitted. These impulses are introduced to an amplifier 32 and may be transmitted at a distance in any well-known manner. The output 33 of the amplifier 32 is shown schematically connected to a switch 34 which, when contacting point 35, transmits the signal impulses directly to the transmission line 36. This line may be a telephone line; or the impulses may be introducedto a carrier telephony or telegraph line system. I have schematically indicated a system whereby the amplified impulses according to my invention may be transmitted by radio.

. Thus, when the switch 34 contacts with point 31,

The modification I have described in connection with Figure 1, is an electro-mechanical vibratory means for translating picture impulses of varying intensities impinging on a photo-sensitive cell which impulses are of substantially constant amplitude but of varying frequency. These impulses may be directly transmitted by line wires or be radiated by ordinary radio methods. The

. facsimile signals corresponds to the audio-frequency modulation of a radio frequency carrier wave as used in any audio-frequencybroadcasting station. No special equipment is required by such stations. for the facsimile broadcasting. The impulses which are induced in thetransformer secondary winding 3| may be applied to the ordinary speech input circuits of radio broadcasting systems and betransmitted as though they were audio signals. I have herein provided for white areas of transmitted pictures to correspond to zero facsimile signal, that is,. no modulation of the carrier wave will then occur. During the black portions of the picture being scanned, the highest (predetermined) frequency of facsimile signal is transmitted according to my invention. This frequency may, for example, be 4000 cycles or any other predetermined frequency according to the design and the speed of transmission desired. Frequencies of the order of 100 cycles would cause relatively slow impulses and correspond toan area which is practically white when reproduced as hereinafter described.

Figure 2 shows another method whereby I cause facsimile signals of amplitude proportional'to the varying intensity of the scanning light beam 5 reflected from the picture 2 to produce corresponding signals of constant intensity but vary ing frequency. The output of photo-electric cell l' is connected to amplifier 6, the output 1 of which is connected to solenoid 43. The amplifier 6 and its output connections 1 are the same as described hereinabove in conjunction with Figure 1. The solenoid 43 has two coils, 43a and 43b, connected as are the coils 8a and 8b of Figure l to the amplifier 6 output leads 1. A plunger 44 is attracted up into the solenoid 43 in varying degree in accordance with the facsimile signal strength as hereinbefore explained. I show a spring 45 and transverse pin 46 on the plunger 44. An extension 49 of the plunger 44 is suitably linked at 50 to a lever 5|. A boss 52 at the end of lever Si is secured to the-variable condenser shaft 53 of a beat frequency oscillator 54, shown schematically. I

The variable condenser used to control the frequency of the output of the a frequency oscillator 54 is purposely shown in perspective to make clear the action of the plunger 44 on it. The variable condenser rotor plates 55 are rotated by the condenser shaft 53 with respect to the stator plates 55'. The tank'circuit 56, including the variable condenser, is part of the variable high frequency oscillatory circuit 51. The tank circuit 58 is part of the fixed high frequency oscillator 51'. As is well known in the radio communication art, the outputs of the two high frequency oscillators are combined and introduced to a detecting stage, and the difference or beat frequency is filtered at the output of a beat frequency oscillator. where the variable frequency is induced to coupling coil 56, and the fixed frequency is induced to coupling coil 58, said coils being connected in series with the primary 59' of transformer 59. The combined signals are introduced to a square-law detector stage 50, where the two original fre- I have shown a simple arrangement quencies as well as their sum and'difference frequencies are produced at its output. A filter ll, connected to the output of the detector 30 is designed to pass the low frequencies, corresponding to the difference or beat frequency of the two original high frequencies to the output I! of the unit 54.

The lever BI is preferably designed to operate over a relatively small arc, of the order of 20 to 30 degrees, in order that the amplitude of the excursion of plunger 44 may be sumciently small so as to permit it to be designed to faithfully follow rapid picture shading variations. The motion of the plunger 44 is linked to the variable condenser shaft 53, as already described, and the rotor plates 56 will correspondingly change the capacitance of the variable condenser to vary the frequency of the oscillator circuit 51. The frequency of the beat frequency oscillator output is in this manner varied in accordance with the shading of the picture being transmitted.

When a black segment of the picture is scanned, no current is impressed on amplifier 3, and the plunger 44 is in its lowest position. The corresponding position of the rotor plates 53 may be made to correspond to a beat frequency output frequency, for example, of 4000 cycles or any other frequency depending upon the speed of transmission desired. When a white picture segment passes the scanning beam and a strong signal flows into amplifier 6, the plunger is moved to its uppermost position and its excursion is made to correspond to an arc of movement of the lever ii in the order of 20 to 30 degrees correspondingly rotating the shaft 53 and the rotor plates 59.

The electrical constants of the beat frequency oscillator are designed so that this relatively small arc of motion of the variable condenser rotors 55 will change the beat frequency output from, for example, 4000 cycles to a lower frequency of, for example, 100 cycles. Since the frequency of excursion of the plunger 04 is relatively high, care must be exercised in design of the mechanical system comprising the plunger N and its extension 49 and the co-acting lever 5i as well as the rotor plates 55 mounted on shaft 53. Provision must be made for a minmium of friction in the movement of the shaft 53, and well oiled bearings or roller bearings should be used. The relative masses and compliances of the components of this moving mechanical system should be designed to avoid mechanical resonances in the range of frequency of mechanical vibration of this system by well known mechanical design methods.

The output 62 of the beat frequency oscillator 54 is coupled to the amplifier 32 by the transformer 28. The output 33 of the amplifier 32 may be transmitted over a line wire or caused to modulate a radio frequency carrier and radiated through an antenna system similar to the system described in connection with Figure 1 hereinabove. The beat frequency oscillator 54 is designed to have a voltage output characteristic of constant amplitude with varying frequency. Thus, the modification embodied in Figure 2 translates the varying picture currents to signals of constant amplitude but frequency varying in accordance with the shading of the picture being transmitted.

When a negative picture is being transmitted and a positive picture is to be reproduced at the receiving end, or when an actual picture is being transmitted and a negative of it is to be reproduced at the receiving end, the modifications according to Figure 2 may be designed to cause this eflect in the following manner:

when the plunger 44 is attracted into the solenoid 43 as a picture segment is being scanned. the rotor plates ll may be arranged to cause an increase inthe beat frequency oscillator ll output instead of decreasing the frequency as hereinabove described. Accordingly, when a black portion of the picture is being scanned, the plunger 44 is not attracted up into the solenoid l3 and the low frequency, for example, cycles is then produced by the beat frequency oscillator II. By thus reversing the relative action of the system, negatives of pictures are transmitted for a positive received picture and vice versa.

.A receiving system for recording the picture impulses as transmitted according to the modifications of Figures 1 and 2, is illustrated in Figure 3. I shall show the receiver in connection with radio transmission of the facsimile signals although connections to line transmission may equally well be adapted by those skilled in the art. A receiving antenna 33 receives the radio signal and introduces it to an ordinary radio receiver 64. By means of switch it normally connecting to contact 06 so that the loud speaker 81 is connected to the radio set by leads I, the output of the receiver may be switched to the contact 68 so that facsimile signals which are received and detected may be connected by leads I0 to the picture reproduction unit ll.

Unit ll comprises an electro-magnet structure 12 with a winding 13 which is connected by leads 14 to a direct current source available in any radio receiver. A circular core 15 forms a circular air gap 18 with the inside rim 11 of the soft iron magnet structure 12. This construction is similar to an ordinary electrodynamic unit of the present type electrodynamic loud speakers. The movable coil II wound on form I! is interposed in the air gap 13. This coil form II is compliantly connected upon the core II by means of the resilient membrane Ill which is mounted on the post ll attached to the core II. A suitable marker 82 is held in a retainer 83 which is connected to the suspended movable coil system by the conical extension 34. The signal currents which are detected by the receiver 84 correspond to the signals of constant amplitude and varying frequency which modulate the transmitting carrier wave. The output of the receiver 64 is connected to the movable coil 18 by leads Ill.

The detected facsimile signals produce alternating currents of constant amplitude in the movable coil 18 and cause it to vibrate in the air gap due to the magnetic reaction with the steady electro-magnetic flux in the air gap 13. The marker 82 is correspondingly caused to vibrate and produce marking impulses of varying frequency. The marking energy of each impulse is substantially the same. As the reproducing unit II is moved along the paper 85, a series of short marks or dots are made on the paper II. The unit H is moved across the sheet of paper in synchronism with the scanning of the picture being transmitted, to build up the received picure.

I have not shown any synchronizing means because any one of many well known in the art may be employed. The reproducing unit ll may traverse the paper sheet 35 in an arced path which is part of the circle in which the whole unit I! rotates through. In a co-pending application, I describe in detail a method for scanning and also reproducing a picture by imparting a rotary motion to the-reproducing means similar to H by a plurality of such units as H being rotated so that as one unit completes marking, another unit starts marking at the beginning of the next line. However, I herein schematically indicate the circular motion imparted to unit H as follows: An arm 86 is bolted to the unit H and fastenedto a beveled gear 81 attached to its shaft 88 which is rotatably supported by bracket 89. A coacting beveled gear 90, rotated by its shaft 9| imparts the continuous circular motion to the unit H. In this application, I amnot concerned with methods for synchronizing and details for the action of any particular system of scanning.

The system of transmission according to my invention as hereinabove described, transmits facsimile signals of constant amplitude. Y In systems utilizing amplitude modulation, the shading of the reproduced picture depends upon the relative magnitude of the received facsimile signal. The vagaries of radio transmission, particularly fading, impair the quality of the received picture because it distorts the relative signal strength received over a period of time. With my system of constant amplitudetransmission, no such defect occurs because the shading of the reproduced picture depends upon the frequency of the marking impulses or dots. An ordinary automatic volume control circuit employed in a radio receiver is entirely satisfactory for reproducing clear and well defined pictures.

A further advantage of my facsimile system is that the received picture is built up with a plurality of discrete marking impulses or dots and is directly applicable for use in printing as in newspaper work. The marker 82 may well be a small chisel or etching tool for engraving the signal impulses directly on a zinc plate. The

zinc plate is then used in connection with printing presses or other inking or reproducing mechanisms in a manner well known in the printing art. The negative of the desired picture should be translated on the zinc plate for positive printing of the picture.

My system may similarly be used with other types of marking or image recording means. The method I describe in my Reissue Patent No. 19,575 of electrolytic photographic recording on special chemically treated paper; or the use of a blunt marker 82 for impacting a carbon sheet or inked ribbon placed above an ordinary paper sheet; or the use of a marker 82 comprising a pencil point or inking stylus may be employed. The actual methods for scanning, recording or synchronizing do not form part of the present invention and any combination of well known methods may be used embodying the principles of the present invention.

A further modification for a transmitting system wherein facsimile signals of amplitude varying in accordance with the shading of the picture being transmitted are converted to corresponding constant amplitude signals of varying frequency is shown in Figure 2a. This .is a modification using a beat frequency oscillator as in Figure 2 but providing for a variable frequency tank circuit wherein the capacitance to be varied is in the form of a flexible flat plate or disc spaced from a fixed plate.

Referring to Figure 2a, the light beam 5 of varying intensity impinges upon photo-electric cell I which produces corresponding signal variations at the input of the amplifier 6'. This amplifier 8' may be any suitable direct current amplifier with two ordinary output load I connecting to the movable coil 18 of the electrodynamic unit .I I. This unit is constructed similar to the unit II in Figure 3 and like numerals refer to corresponding elements. The beat frequency oscillator 54 circuit is schematically represented as in Figure 2, and like numbers refer to similar components.

A flexible metallic disk 20l is mounted with respect to the metallic casing 200 and insulated therefrom so that a capacitance exists between the casing 200 and the disk 20!. The disk 20| is supported between the stretching rings 202 and 203 which are insulated from the casing 200 by means of insulation 204. Bolts 205 pass through the insulating bushing 201, and have nuts 206 for holding the disk stretching structure in position. The nuts 206 press against insulating washers, 208. The condenser 2I3 accordingly comprises a stretched disk 20l spaced from a casing 200. Leads 209 and 2|0 connect this condenser M3 to the variable frequency tank circuit 58 of the beat frequency oscillator 54. A pin 2 mechanically connects the movable member 84 of the electrodynamic unit H to the stretched disk 20| at its center 212.

The varying light intensity resulting from the shadin'gof the picture being scanned causes corresponding excursions of the movable coil 18 which transmits its motion to disk 20! with pin 2. The capacity of the condenser H3 is accordingly varied and correspondingly changes the frequency of the variable frequency oscillator 51 in a manner well known to those skilled in the art. The frequency at the output 62 of the beat frequency oscillator 54 is therefore varied in accordance with the shading of the picture signal being transmitted in a manner hereinabove explained in connection with Figure 2. The output 62 of beat frequency oscillator 54 is coupled to the amplifier 32 transformer 28 and may be transmitted over a land line 36 or modulate a radio frequency carrier for radio broadcasting as hereinabove described.

It is possible with the embodiment of Figure 2a to design a facsimile transmission system of greater speed as compared to that of Figure 2, since the moving elments of the translation from amplitude to frequency modulation means, namely the movable coil 18, element 84 pin 2 and flexible disk 20l are much smaller and lighter than the corresponding plunger 44, lever 5| and variable condenser 55. The design of the beat frequency oscillator 54 to utilize the comable condenser 2 B to produce corresponding output audio frequency variations from, for example, 4000 cycles to a hundred cycles according to the picture shading may be readily accomplished by those skilled in the communications art. .The filter section of the beat frequency oscillator 54 is designed to pass through a band of signals corresponding to the predetermined signal range, for example, 4000 to 100 cycles, and no other frequency signals.

The principle which forms the basis of my invention may equally well be applied directly at the receiver. Transmitted amplitude modulated facsimile signals may be converted to marking impulses of constant intensity and, varying frequency in such a receiver. A great advantage of such a system in conjunctionvwith the paratively small capacitance changes of the varireproduction of amplitude modulated facsimile signals is that the energy for the marking impulses is locally generated and the received facsimile signals are used to produce the half-tone or shading effects in the reproduced picture by varying the frequency of the local marking im-' pulses. The reproducer is a rugged, cheap and simple device and operates very efficiently with respect to the trength of the incoming signals. A clear cut picture is reproduced by impulses of constant strength and the effects of fading in radio reception upon the appearance of the reproduced picture are greatly minimized.

Figure 4 is a schematic illustration of a commonly used amplitude modulated facsimile signal system. A spot of light from source 4 is concentrated upon the picture 2 mounted upon the drum 3 and is reflected along a beam 0 to the cell I. An amplifier 0 is used to amplify the photo-electric impulses in cell I and impress them upon a transmitting system similar to that used in Figure 1 through the coupling transformer 20. The amplitude modulated facsimile i signals are further amplified at 02 and may be alternatively transmitted by means of the land line 00 or used to modulate a radio frequency carrier wave transmitter. A light chopper 00 is used to interrupt the reflected beam 0 at a constant frequency so that ordinary amplifiers and receivers may be used as is known by those skilled in the art.

The amplitude modulated facsimile signals are impressed upm the radio frequency carrier wave transmitted by the antenna 42 of the radio transmission system schematically shown in Figure 4 and are received by the local antenna 03 of an ordinary radio receiver 04 as illustrated in Figure 5. The amplitude modulated facsimile signals transmitted by the system of Figure 4 are polarized so that a darker picture element will produce an increased signal amplitude, and a brighter picture element, will cause a decreased signal amplitude. The output of the receiver 04 .s switched from the speaker to the leads I0 by means of switch 60 during facsimile reproduction. The detected facsimile signals, corresponding to the original modulating impulses at transformer 20 of Figure 4, are then passed through a suitable rectifier I00. For rugged, cheap, simple and portable use, I prefer to employ a copper-oxide rectifier for further rectifying the facsimile signals and forming a substantially uni-directional energization of the solenoid I02a of the facsimile reproducer I00.

The solenoid I02 comprises the two coil sections I02a and I02b. An adjustable direct current is passed through the coil I02b to attract the plunger up into the solenoid I02. The polarity of the uni-directional current through 0011 I02a is connected so that the magnetic flux produced by the coil I02a counteracts thesteady magnetic attraction of coil I02b to permit the mechanically biased plunger I04 to be lowered. When a strong signal enters coil I02a, corresponding to a dark picture segment, the plunger I04 assumes its lowest position with respect to the electro-magnet I I5.

The reproducer I03 has a construction very similar to the corresponding electro-mechanical unit of the transmitter in Figure 1. A plunger I04 mechanically biased by spring I00 has a transverse pin I00 which abuts theedges I01 of insulation member I00. A projection I00 in member I00 limits the upward excursion of the armature II2. A metallic extension I00 of the plunger I04 carrie sacontact point III for coacting with the contact spring III attached to the armature I I2. when no signal is received by solenoid I020, corresponding to a white element of the picture being transmitted, the plunger I04 will be positioned up in solenoid I02 so that the armature II2 will stop vibrating due to the pre-- vention of the contact between point III and spring III. with signal current through am lenoid I02, the contact point IIO moves down so that it contacts contact spring III. The armature II 2 is attached to the metal spring I II which is secured to the post H4.

The electro-magnet III is connected in series with a battery or direct current source II, together with a rheostat III through the flexible connection III to the contact point H0 in series with the contact spring III and the armature II2 through the metallic spring III and metallic post I I4 back to the electro-magnet I I0 by means of connection H0. This local electromechanical circuit I20 operates at its predetermined highest frequency when maximum signal passes through the electro-magnet I02 and the plunger I04 is in its nearest position with respect to the electromagnet H5. A retainer I2I holding a marker I22 is mounted at the end of the armature 2. A sheet I20 upon which the picture is to be reproduced is shown mounted upon a drum I24 which rotates in synchronism with the transmitting drum 0. The energy of the marking impulses is locally controlled by means of the rheostat II! in the electro-mechanical circuit I 20.

The electro-magnet III may very well be positioned at one side of the vibrating armature II2 instead of beneath it, to permit the armature II2 to be mounted nearer to the sheet being marked.

I have accordingly shown a modification of the electromechanical system I20 in Figure 6 where the electro-magnet H5 is placed at a side of the armature H2 and the poles I20 of this electromagnet are extended underneath the armature II2. These Poles I20 may be bent as illustrated so that the centers of. the coils I20 are above the level of the poles I25.

Figure 7 is a sectional view through a preferred embodiment of the reproducing unit employing the principle schematically shown in Figure 6. A housing I21 encloses the reproducing unit I00 and is integrally formed with member I00. The member I00 has a recess enclosing the spring I04 and the transverse pin I00 similar to Figure 5. The solenoid I02 is mounted between the member I00 and the cover plate I20. The metal post I I4 is set in the housing and supports the vibrating armature. The poles I20 of the electro-magnet are shown set in the bottom of the structure. The coils I20 of the electro-magnet II! are shown with their centers above the poles I20 so that a minimum distance is obtained between the bottom I20 of the reproducing unit I20 and the vibrating armature H2. The retainer I2I and marker I22 project from the end of the armature 2. A sheet I00 is fed underneath the marking stylus I22 in any well known manner. The sheet I20 may be mounted on a drum or fed continuously from a roll at a predetermined rate.

A hollow shaft IOI is affixed to the reproducing unit I00 as illustrated in Figure 7. The leads connecting to the solenoid I02, the contact point H0 and the electro-magnet II! are passed through the hollow shaft III to form connections to the corresponding parts of the receiving circuit of Figure 5. The reproducing unit I0! is caused aoeaws to traverse over the surface of the paper I30 in synchronism with the scanning beam on the transmitted picture. Although as in the other embodiments, any preferred method for scanning and synchronizing may be employed, I have schematically illustrated a drive system for this reproducing unit I03 similar to that shown in connection with Figure 3. The shaft I3I is fastened to a shaft I32 on which is mounted the bevelled gear I33. A bracket I34 and sleeve I34 rotatably support the gear I33. A coacting bevelled gear I35 transmits the rotating drive power from shaft I36 to rotate the reproducing system I03 as explained in connection with the embodiment of Figure 3 hereinabove.

A further embodiment in the application of my invention is illustrated in the receiver of Figure 8. The facsimile signals from the receiver 64 which are further rectified by the copper oxide rectifier I00 is introduced to the solenoid I40 by means of the leads IN. The solenoid ofthis embodiment is used to transmit the effect of its attraction on the plunger I4I to the contact point I42 by means of a lever I43 which is supported on an axis I44. The excursion of the contact point I42 is generally small for the vibrating electromechanical system. By suitable lever arrangement, the excursion of the plunger I4I may be made several times that of the contact point I42. The lever system I44 produces a mechanical advantage so that a positive control of the contact point I42 is had over the small excursions of contact I42 by relatively greater excursions of the plunger I4I.' It may be advantageous to slightly curve the plunger HI and its solenoid I40, as illustrated in Figure 8. Suitable mechanical stops I45 and I46 are arranged on either side of the vibrating lever I43. A spring I41 is used to mechanically bias the contact point I42 away section view. The local electromechanical circuit I20 is similar to that of. Figure 5, and like numerals refer to like parts. The relative masses and compliances of the components of this dynamic mechanical system are designed so that no mechanical resonances occur in the operating frequency range and the relative mechanical impedances of the co-acting mechanical parts are matched for maximum translation efficiency.

The embodiment of Figure 8 is shown constructed in such manner that when a positive of the original picture is received, a negative reproduction will result if black areas correspond to maximum transmitted facsimile signal strength. When a dark area is being scanned, relatively large current will flow through the solenoid coil H011 and repel the plunger IM to move the contact I42 away from the electromagnet II5 to decrease the frequency of vibration of the armature II2. .A stylus connected at the end of this armature may be used to directly engrave a zinc plate to produce the required negatives for newspaper printing of the facsimile reproduction or other recording means may be employed. By mechanical rearrangement, the lever system between the plunger MI and the contact point I42 may be adapted f0]; reproducing "positive pictures when receiving positive facsimile signals.

Figures 9 and 10 are illustrations of further modifications which are particularly useful in facsimile transmission systems where black and white pictures are to be transmitted. My principle of utilizing local energization for the marking impulses is further simplified when the mark- I50 on a coil form I53.

ing impulses, are of only a constant frequency corresponding to black picture segments, and of zero frequency (no marking) corresponding to the white picture segments. In Figure 9 the receiving system shown is similar to that of Figures 5 and 8. The rectifier I00 converts the facsimile signals to uni-directional direct current which is conducted to the movable coil I50 of the electrodynamic reproducing unit I5I by leads IOI. Another movable coil I52 is wound adjacent to coil This coil I52 is connected to a local oscillating circuit I54 through the potentiometer I55. The remainder of this electrodynamic reproducing unit I5I is identical with the unit H of Figure 3 andcorresponding parts have been labeled with the same number.

The energy for the marking impulses is locally supplied at a predetermined frequency by an alternating current generator I54. The leads 14 of the coil13 connect to the direct current source I56 through a rheostat I51. the marking impulses is adjusted by either the position of the arm I58 on the potentiometer I or by the adjustment of the rheostat I51 or both. The alternating current locally produced in the movable coil I52 reacts with the steady magnetic field in the air gap 1.6 to vibrate the stylus 82 connected at the end of the movable oil system. When no current flows through signal coil I50, the marking impulses proceed at a predetermined frequency for example, 4000 cycles, and producesa plurality -of close dots on the paper which correspond to a black segment of the transmitted picture. When a white segment is being scanned, a facsimile signal will result in a direct current flow through the rectifier I00 and the coil I50. The polarity of the direct current through the coil I50 is connected so that the action of the coil I50 is to decrease the strength of the downward or marking impulse by a degree sufficient to avoid an actual mark upon the paper 85 and a corresponding white portion is obtained. The reproduced figure or facsimile message is composed of dark and white sections. The dark section is a plurality of discrete dots or marks closely spaced. The facsimile signals are accordingly superimposed on a local marking circuit to act as an interrupter of the marking action. The translation efficiency is greatly increased by using such a negative action facsimile reproduction means.

In Figure 10, I have illustrated a further modification of the negative action principle described in connection with Fig. 9. The radio receiver 64 and rectifier I00 is similar to that of Fig. 9 and the rectified facsimile signals are introduced to the winding I60 by leads MI. The winding I60 is wound on a soft iron core I6I. Another winding i62 on the core I6I is connected to a direct source I63, through rheostat I64. The attraction for the armature I61 by the electromagnetic action of coil I62 on core I6I is adjustable by varying the biasing current by means of the rheostat I64. A local oscillator I65 passes alternating current of predetermined frequency through the winding I66 on the core I6I.

The armature I61 is compliantly mounted on post I69 by spring I68. A spring I10 fixed at one end to the member I", mechanically biases the armature I61 away from the electromagnet core I6I. A projection I1I' in member I1I limits the excursion of the armature I61 upwards. Amarker I13 is secured to the end of the armature I61 by the retainer I12. A sheet I14 is wound on drum I'll similar in the other systems hereinabove described.

The action of the local oscillator I" is to cause a varying attraction on the armature I81 and produce marking impulses-of the marker I" on the sheet I'll, at the predetermined frequency. As the sheet moves with respect to the vibrating marking system, a succession of closely spaced marking dots or impulses are formed thereon. The strength of the marking impulses is adjusted by varying the biasing direct current with rheostat I. flowing through the winding IBI is polarized so that it bucks the attraction of the armature due to the local direct current in winding I82. When a facsimile signal corresponding to a white message area is received, it will buck the attractive force on the armature I61, and result in no marking imprint by the marker I13 on the sheet I".

I have described in detail several embodiments and modifications of a system of facsimile transmission and reproduction which follow from the principles of my invention. Many variations may be made by those skilled in the art which would come within the scope of my invention, and I do not intend to be limited except as set forth in the following claims.

I claim:

1. In a signaling system, means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents comprising a solenoid, an electromechanical vibrator having an armature and a variably positioned contact member for changing the frequency of vibration of said armature, means for mechanically regulating the position of said contact member by said solenoid, said solenoid being electrically connected to said varying amplitude currents, a transformer and a source of current, said contact member and said armature being circuitally connected with a winding of said transformer and said source whereby alternating current of frequency varying in accordance with the frequency of vibration of said armature is induced to the output of said transformer.

2. In a signaling system, means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency, and substantially constant amplitude audio frequency currents comprising a solenoid, said solenoid being electrically connected to said varying amplitude currents, an oscillator circuit including a variable condenser for varying the frequency of the alternating current-output of said oscillator, a second oscillator circuit for generating alternating current of substantially fixed frequency, means for beating the alternating current outputs of said first and second oscillators, filter circuit means for passing through the audio frequency currents from said beat frequency means and means including mechanical connections controlled by said solenoid for varying the capacitance of said variable condenser in accordance with said varying amplitude currents.

3. In a signaling system, means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents comprising an electrodynamic unit having a coil movable in a substantially uniform magnetic field, said movable coil being electrically connected to said varying amplitude currents and an oscillator circuit includ- The rectified facsimile signal current ing a variable condenser for varying the frequency of the alternating current output of said oscillator; a second oscillator circuit for generating alternating current of substantially fixed frequency, means for beating the alternating current outputs of said first and second oscillators, filter circuits means for passing through theaudio frequency currents from said beat frequency means and means including mechanical connections controlled by said movable coil for varying the capacitance of said variable condenser in accordance with said varying amplitude currents.

4. In a signaling system means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents comprising electromechanical means responsive to said varying amplitude currents, a first oscillator circuit including a variable condenser for varying the frequency of the alternating current output of said oscillator, 'means including mechanical connections controlled by said electro-magnetic means for varying the capacitance of said variable condenser, a second oscillator circuit for generating an alternating current of substantially fixed frequency, and means including circuit connections for beating the alternating current outputs of said first and second oscillators to produce said varying audio frequency currents.

5. In a signaling system means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents comprising a solenoid electrically connected to said varying amplitude currents, a plunger controlled by said solenoid, a first oscillator circuit including a variable condenser for varying the frequency of the alternating current output of said oscillator, means including mechanical connections controlled by said plunger for varying the capacitance of said variable condenser, a second oscillator circuit for generating an alternating current of substantially fixed frequency, and means including circuit connections for beating the alternating current outputs of said first and second oscillators to produce said varying audio frequency currents.

6. In a signaling system means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents comprising an electrodynamic unit having a coil movable in a substantially uniform magnetic field, said movable coil being electrically connected to said varying amplitude currents, a first oscillator circuit including a variable condenser for varying the frequency of the alternating current output of said'oscillato'r, means including mechanical connections controlled by said movable coil for varying the capacitance of said variable condenser, a second oscillator circuit for generating an alternating current of substantially fixed frequency, and means including circuit connections for beating the alternating current outputs of said first and second oscillators to produce said varying audio frequency currents.

7. In a signaling system means for translating a band of audio frequency currents of varying amplitude into a band of corresponding varying frequency and substantially constant amplitude audio frequency currents, comprising a solenoid electrically connected to said varyingiamplitude currents, a, plunger controlled lay said solenoid, a first oscillator circuit including a variable condenser for varying the frequency or the alternatin: current output of said oscillator. said variable v condenser having a. rotor section, said rotor section being mechanically controlled by said. plung er Iorvarying the capacitance of said condenser,

a second oscillator circuit for generating an alternating current of substantially fixed frequency, and means including circuit connections for heating the alternating current outputs of said first and second oscillators to produce said varying 5 audio frequency currents.

WILLIAM G. H. FENCE. 

